Aromatic polyester resins have long been known. For instance, p-hydroxy benzoic acid homopolymer and copolymers have been provided in the past and are commercially available. Those aromatic polyesters normally encountered in the prior art have tended to be somewhat intractable in nature and to present substantial difficulties if one attempts to melt process the same while employing conventional melt processing procedures. Such polymers commonly are crystalline in nature, relatively high melting or possess a decomposition temperature which is below the melting point, and when molten frequently exhibit an isotropic melt phase. Molding techniques such as compression molding or sintering may be utilized with such materials; however, injection molding, melt spinning, etc., commonly have not been viable alternatives or when attempted commonly have been accomplished with difficulty. Such polymers commonly cannot be melt extruded to form nondegraded fibers. Even those aromatic polymers which exhibit a melting point below their decomposition temperature commonly melt at such high temperatures that quality fibers may not be melt spun. For instance, fibers melt extruded at extremely high temperatures commonly possess a voidy internal structure and diminished tensile properties.
Representative publications which discuss aromatic polyesters include: (a) Polyesters of Hydroxybenzoic Acids, by Russell Gilkey and John R. Caldwell, J. of Applied Polymer Sci., Vol. II, Pages 198 to 202 (1959), (b) Polyarylates (Polyesters from Aromatic Dicarboxylic Acids and Bisphenols), by G. Bier, Polymer, Vol. 15, Pages 527 to 535 (August 1974), (c) Aromatic Polyester Plastics, by S. G. Cottis, Modern Plastics, Pages 62 to 63 (July 1975), and (d) Poly (p-Oxybenzoyl Systems): Homopolymer for Coatings: Copolymers for Compression and Injection Molding, By Roger S. Storm and Steve G. Cottis, Coatings Plast. Preprint, Vol. 34, No. 1, pages 194 to 197 (April 1974). See also, U.S. Pat. Nos. 3,039,994; 3,169,121; 3,321,437; 3,553,167; 3,637,595; 3,651,014; 3,723,388; 3,759,870; 3,767,621; 3,778,410; 3,787,370; 3,790,528; 3,829,406; 3,890,256; and 3,975,487.
Also, it more recently has been disclosed that certain polyesters may be formed which exhibit melt anisotropy. See for instance, (a) Polyester X7G-A Self Reinforced Thermoplastic, by W. J. Jackson, Jr., H. F. Kuhfuss, and T. F. Gray, Jr., 30th Anniversary Technical Conference, 1975 Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., Section 17-D, Pages 1 to 4, (b) Belgian Pat. Nos. 828,935 and 828,936, (c) Dutch No. 7505551, (d) West German Nos. 2520819 and 2520820, (e) Japanese Nos. 43-233, 3017-692, and 3021-293, and (f) U.S. Pat. Nos. 3,991,013; 3,991,014; 4,067,852; 4,075,262; 4,083,829; 4,118,372; and 4,130,545. See also commonly assigned U.S. Ser. Nos. 843,933, filed Oct. 20, 1977; and 877,917 filed Feb. 15, 1978.
U.S. Pat. Nos. 3,991,013 discloses inter alia a specific polyester derived from 1,2-bis(para-carboxyphenoxy) ethane, terephthalic acid and substituted hydroquinone. Optionally, some unsubstituted hydroquinone may accompany the required substituted hydroquinone reactant when forming the specific polyester there disclosed.
It is an object of the present invention to provide an improved melt processable polyester which exhibits an anisotropic melt phase.
It is an object of the present invention to provide a novel melt processable polyester which can be produced on a relatively economical basis.
It is an object of the present invention to provide an improved polyester which is suited for the formation with ease of quality melt extruded fibers, molded articles, and melt extruded films.
It is an object of the present invention to provide an improved melt processable polyester capable of forming an anisotropic melt phase at a temperature no higher than approximately 320.degree. C., preferably below approximately 300.degree. C., and most preferably below approximately 290.degree. C.
It is an object of the present invention to provide a novel polyester which is capable of melt processing in standard equipment commonly utilized with polyethylene terephthalate.
It is an object of the present invention to provide an improved polyester which forms a low viscosity highly tractable melt phase.
It is an object of the present invention to provide an improved polyester which forms an anisotropic melt phase at a temperature well below its decomposition temperature and which may form quality high performance fibers.
It is an object of the present invention to provide improved polyester fibers which particularly are suited for use as fibrous reinforcement in a rubber matrix.
It is another object of the present invention to provide an improved polyester which readily may be melt extruded to form a film.
It is another object of the present invention to provide an improved polyester which readily may be injection molded to form a molded article (which optionally may be fiber reinforced) exhibiting superior tensile strength, flex strength, and impact strength.
It is another object of the present invention to provide novel polyester fibers which exhibit tenacity values which are enhanced to a surprisingly great extent upon thermal treatment.
These and other objects, as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following detailed description.